I have condensation drain from a humidifier that vents outside. On cold days, this water freezes and backs up into the basement. I've heard of a tap into a sewer line. I'm looking for the parts to do this job.

You do not connect directly to the sewer. You use a "indirect waste" connection. All that means is that you terminate the AC line a few inches above a floor drain or a laundry sink. That way a trap isn't needed. And you can avoid cutting into the house drainage. Good luck, Tom